GCSE Maths Foundation

GCSE Maths Foundation · AQA · Order of operations & negatives

Squaring a negative: (−8)² = 64, and −4² is not (−4)²

Squaring a negative trips students two ways. First, they keep the minus, writing (−8)2=−64(-8)^2 = -64 when squaring multiplies the number by itself and a negative times a negative is positive, so (−8)2=64(-8)^2 = 64. Second, they read −42-4^2 and (−4)2(-4)^2 as the same, when the bracket decides: (−4)2=16(-4)^2 = 16 but −42=−16-4^2 = -16.

The thirty-second fix: squaring a negative always gives a positive, because the two minus signs cancel — and the bracket decides what gets squared, so −4² means −(4²) = −16, while (−4)² squares the whole −4 to give 16. So (−8)2=64(-8)^2 = 64, and the killer pair is −42=−16-4^2 = -16 versus (−4)2=16(-4)^2 = 16.

Ready to fix this? The Order of operations & negatives lesson works through this misconception and the others in Order of operations & negatives, one altitude at a time.

How to spot it in your own work

  • You kept the minus on a square, writing (−8)2=−64(-8)^2 = -64 instead of 64 — a negative times a negative is positive.
  • You read −42-4^2 and (−4)2(-4)^2 as the same, when they are −16-16 and 1616.
  • You squared the whole of −42-4^2 as if it were bracketed, getting 16 instead of −16-16 — without a bracket the square reaches only the 4.
  • You substituted a negative into x2x^2 and left the answer negative, e.g. taking (−3)2(-3)^2 as −9-9 rather than 99.

An exam question that triggers it

Here is a typical AQA Foundation question of this shape (non-calculator paper, work out the value):

Work out

(−8)2(-8)^2

The misconception is to carry the minus through and write −64-64, as if squaring kept the sign. But squaring means (−8)×(−8)(-8) \times (-8), and a negative times a negative is positive.

The two minus signs cancel: (−8)×(−8)=64(-8) \times (-8) = 64. Squaring any negative gives a positive result.

Why students fall for this

A minus sign feels like it should travel with the number, so squaring it looks like it ought to keep it — hence −64-64. But squaring is multiplying the number by itself, and (−8)2=(−8)×(−8)(-8)^2 = (-8) \times (-8). Two negatives multiplied give a positive, so the minus signs cancel and the answer is +64+64. Every squared negative comes out positive for the same reason.

The bracket version is sharper. −42-4^2 and (−4)2(-4)^2 look almost identical but are not equal, because powers are worked out before the minus is applied unless a bracket forces the minus inside first. Without a bracket, −42-4^2 means −(42)=−16-(4^2) = -16: square the 4, then apply the minus. With a bracket, (−4)2(-4)^2 makes −4-4 a single value that is squared, so (−4)×(−4)=16(-4) \times (-4) = 16.

AQA Foundation papers exploit both directly: evaluating a bracketed square like (−8)2(-8)^2, and substituting a negative into an expression with x2x^2 where the bracket — or its absence — fixes the sign.

Worked example — the killer pair. Work out −42-4^2 and (−4)2(-4)^2.

No bracket means the square reaches only the 4; a bracket means the whole −4-4 is squared:

−42=−(42)=−16(−4)2=(−4)×(−4)=16-4^2 = -(4^2) = -16 \qquad (-4)^2 = (-4)\times(-4) = 16

The trap is to treat them as the same. They differ only by the bracket, and the bracket is the whole point: −16-16 against 1616.

The fix: Squaring a negative gives a positive; the bracket decides what gets squared

Squaring multiplies the number by itself. (−8)2=(−8)×(−8)(-8)^2 = (-8) \times (-8), and a negative times a negative is positive, so the answer is 6464 — the minus signs cancel.

A squared negative is always positive. Whatever the digits, (−n)2(-n)^2 comes out positive, because you are multiplying two negatives.

Look for the bracket. With a bracket, the whole negative is squared: (−4)2=16(-4)^2 = 16. Without one, the square attaches to the digit only and the minus stays outside: −42=−(42)=−16-4^2 = -(4^2) = -16.

When substituting, bracket the negative. Putting x=−3x = -3 into x2x^2 means (−3)2=9(-3)^2 = 9, not −9-9 — write the bracket so the square reaches the whole value.

Worked example

Work out (−8)2(-8)^2, then compare −42-4^2 with (−4)2(-4)^2. These are the two traps: keeping the minus on a square, and missing the bracket.

  1. Write the square as a product. (−8)2=(−8)×(−8)(-8)^2 = (-8) \times (-8).
  2. Cancel the signs. A negative times a negative is positive, so
    (−8)2=(−8)×(−8)=64(-8)^2 = (-8)\times(-8) = 64
    The trap answer −64-64 keeps a single minus that should have cancelled.
  3. Square without the bracket. −42-4^2 has no bracket, so the square reaches only the 4: −(42)=−(16)=−16-(4^2) = -(16) = -16.
  4. Square with the bracket.
    (−4)2=(−4)×(−4)=16(-4)^2 = (-4)\times(-4) = 16
    Same digits, opposite signs: −42=−16-4^2 = -16 but (−4)2=16(-4)^2 = 16. The bracket is the whole difference.

So a squared negative is positive whenever the negative is bracketed, and the opening trigger is (−8)2=64(-8)^2 = 64 — not the −64-64 you get by carrying the minus through the square.

Find out if this is costing you marks

The 10-minute diagnostic checks for this pattern (and four others) using AQA-style GCSE Higher items. Free, no signup, anonymous.

Common questions

What is (−8)2(-8)^2?

It is 64, not −64-64. Squaring means multiplying the number by itself, and (−8)2=(−8)×(−8)(-8)^2 = (-8) \times (-8). A negative times a negative is positive, so the two minus signs cancel and the answer is +64+64. Leaving it as −64-64 keeps a single minus sign, but squaring a negative always gives a positive result.

Is −42-4^2 the same as (−4)2(-4)^2?

No. (−4)2=16(-4)^2 = 16, but −42=−16-4^2 = -16. The bracket decides what gets squared. In (−4)2(-4)^2 the whole of −4-4 is squared, so (−4)×(−4)=16(-4) \times (-4) = 16. In −42-4^2 there is no bracket, so by order of operations the square attaches to the 4 only: it means −(42)=−(16)=−16-(4^2) = -(16) = -16. The minus sits outside the squaring.

Why does the bracket change the answer when squaring a negative?

Because powers are worked out before the minus sign is applied, unless a bracket forces the minus inside first. Without a bracket, −42-4^2 is read as −(42)-(4^2): square the 4 to get 16, then apply the minus for −16-16. With a bracket, (−4)2(-4)^2 makes −4-4 a single value that is squared, so (−4)×(−4)=16(-4) \times (-4) = 16. Same digits, opposite signs — the bracket is the whole difference.

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Squaring a negative: (−8)² = 64, and −4² is not (−4)² | GCSE Maths Foundation